Tools

Infusion rate from mcg/kg/min

Pump rate in mL/h for drugs dosed in mcg/kg/min (noradrenaline, adrenaline, dobutamine, milrinone, nitroglycerin by weight).

Dose from pump rate (mcg/kg/min)

Reverse calculation: what dose is the patient receiving at the current pump rate?

Infusion rate from per-kg-per-hour dose

Pump rate for drugs dosed per kg per hour (insulin U/kg/h, midazolam mg/kg/h, propofol mg/kg/h, fentanyl mcg/kg/h, dexmedetomidine mcg/kg/h).

Infusion rate from a fixed hourly or per-minute dose

Pump rate for non-weight-based infusions such as vasopressin (U/min), labetalol (mg/min) or amiodarone (mg/h).

Predicted (ideal) body weight

ARDSNet predicted body weight from height and sex. Use for tidal volume, not for most drug doses.

Adjusted body weight

IBW + 0.4 × (actual − IBW). Used for some drug doses (e.g. aminoglycosides) and nutrition in obesity.

Body mass index

Weight ÷ height². Asian cut-offs differ (overweight ≥ 23, obese ≥ 25 in Indian guidance).

Body surface area (Mosteller)

√(height cm × weight kg ÷ 3600).

Paediatric endotracheal tube size

Internal diameter (mm) = age/4 + 3.5 (cuffed) or age/4 + 4 (uncuffed), for children ≥ 2 years.

Paediatric oral ETT depth at the lips

Oral tube depth (cm at lips) = age/2 + 12 for children ≥ 2 years (≈ 3 × ETT ID).

Paediatric weight estimate (APLS)

1-5 years: 2 × age + 8. 6-12 years: 3 × age + 7.

Tidal volume from predicted body weight

Lung-protective tidal volume (usually 6 mL/kg PBW; range 4-8).

PaO₂/FiO₂ ratio

Oxygenation ratio with ARDS severity bands (Berlin; PEEP ≥ 5 cmH₂O).

SpO₂/FiO₂ ratio

Non-invasive oxygenation ratio; valid only when SpO₂ ≤ 97%. Global ARDS definition uses S/F ≤ 315.

Oxygenation index

OI = FiO₂(%) × mean airway pressure ÷ PaO₂.

Driving pressure

Plateau pressure − PEEP (volume control, passive patient).

Static respiratory system compliance

Vt ÷ (Pplat − PEEP).

ROX index

(SpO₂/FiO₂) ÷ respiratory rate, for patients on HFNC. Assess at 2, 6 and 12 h.

Rapid shallow breathing index

RR ÷ tidal volume in litres during a spontaneous breathing trial.

Alveolar-arterial O₂ gradient

PAO₂ = FiO₂ × (Patm − 47) − PaCO₂/0.8; A-a = PAO₂ − PaO₂.

Oxygen cylinder duration

Minutes of oxygen left at a given flow.

Oxygen cylinder contents (Boyle's law)

Free gas volume ≈ water capacity (L) × gauge pressure (bar). 1 kg/cm² ≈ 0.98 bar; 1 bar ≈ 14.5 psi.

Maintenance fluid rate (4-2-1 rule)

Holliday-Segar hourly maintenance: 4 mL/kg/h for the first 10 kg, 2 mL/kg/h for the next 10 kg, 1 mL/kg/h for each kg above 20.

Burns fluid in first 24 h

mL/kg/%TBSA × weight × %TBSA (partial + full thickness). Half in the first 8 h from the time of burn.

Westley croup score

Severity of croup (0-17).

Clinical Frailty Scale (CFS v2.0)

Baseline frailty 2 weeks before acute illness, scored 1-9. Validated for age ≥ 65.

STOP-BANG

Screening for obstructive sleep apnoea (0-8).

Glasgow Coma Scale

Eye + Verbal + Motor (3-15). Record components, e.g. E3 V4 M5.

qSOFA

Bedside prompt for poor outcome in suspected infection. Not a diagnostic test for sepsis.

SOFA score

Sequential Organ Failure Assessment: 0-4 per organ system, total 0-24. A rise of ≥ 2 from baseline with infection = sepsis.

NEWS2

National Early Warning Score 2 (SpO₂ scale 1).

CURB-65

Severity of community-acquired pneumonia.

Wells score for PE

Pre-test probability of pulmonary embolism.

Richmond Agitation-Sedation Scale

Single-item sedation/agitation score from +4 to −5.

Anion gap

Na⁺ − (Cl⁻ + HCO₃⁻). Correct for albumin.

Albumin-corrected anion gap

AG + 2.5 × (4.0 − albumin g/dL).

Delta ratio

(AG − 12) ÷ (24 − HCO₃⁻). Detects a second metabolic process in a high-AG acidosis.

Expected PaCO₂ (Winter's formula)

Expected PaCO₂ = 1.5 × HCO₃⁻ + 8 (± 2) in metabolic acidosis.

Calculated serum osmolality (Indian units)

2 × Na + glucose (mg/dL)/18 + urea (mg/dL)/6. Uses blood urea, as reported by most Indian labs.

Osmolal gap

Measured − calculated osmolality. Raised in toxic alcohol poisoning.

Sodium corrected for glucose

Na + 2.4 × (glucose − 100)/100 (Hillier; Katz uses 1.6).

Expected Na change per litre of infusate (Adrogue-Madias)

ΔNa = (infusate Na + K − serum Na) ÷ (TBW + 1). Estimate only; recheck Na every 2-4 h.

Free water deficit

TBW × (Na/140 − 1).

Albumin-corrected calcium

Ca (mg/dL) + 0.8 × (4.0 − albumin g/dL). Prefer ionised calcium in ICU.

Creatinine clearance (Cockcroft-Gault)

(140 − age) × weight ÷ (72 × creatinine), × 0.85 if female. Not valid in unstable AKI.

Fractional excretion of sodium

(Urine Na × Plasma Cr) ÷ (Plasma Na × Urine Cr) × 100.

Mean arterial pressure

(SBP + 2 × DBP) ÷ 3 (estimate; use the arterial line value when available).

Shock index

Heart rate ÷ systolic BP.

Corrected QT (Bazett)

QT ÷ √(RR in seconds). Over-corrects at fast heart rates.

Peradeniya Organophosphorus Poisoning (POP) scale

Severity of OP poisoning at presentation (0-11).